Fuel cells produce electricity through electrochemical reaction and have been used as power sources in many applications. Fuel cells can offer significant benefits over other sources of electrical energy, such as improved efficiency, reliability, durability, cost and environmental benefits. Fuel cells may eventually be used in automobiles and trucks. Fuel cells may also power homes and businesses.
There are several different types of fuel cells, each having advantages that may make them particularly suited to given applications. One type is a proton exchange membrane (PEM) fuel cell, which has a membrane sandwiched between an anode and a cathode. To produce electricity through an electrochemical reaction, hydrogen (H2) is supplied to the anode and air or oxygen (O2) is supplied to the cathode.
In a first half-cell reaction, dissociation of the hydrogen (H2) at the anode generates hydrogen protons (H+) and electrons (e−). Because the membrane is proton conductive, the protons are transported through the membrane. The electrons flow through an electrical load that is connected across the electrodes. In a second half-cell reaction, oxygen (O2) at the cathode reacts with protons (H+) and electrons (e−) are taken up to form water (H2O). Parasitic heat is generated by the reactions and must be regulated to provide efficient operation of the fuel cell stack.
The fuel cell stack includes coolant flow fields through which a coolant flows. The coolant is a heat transfer fluid that can warm or cool the fuel cell stack depending on the relative temperatures of the coolant and the fuel cell stack components. Traditional coolant flow fields distribute the coolant at varying rates across the fuel cell stack. As a result, there is a non-uniform temperature distribution across the fuel cell stack. Such non-uniform temperature distributions result in inefficient operation of the fuel cell stack and non-uniform stress loads in the fuel cell stack that can degrade the useful life of the fuel cell stack.
Traditionally, bipolar plates divide adjacent fuel cells. Bipolar plates typically include first and second plate halves that each include a reactant flow field and a coolant flow field formed therein. Stamped bipolar plates include first and second stamped halves that consist of sheet metal that is stamped to define the reactant and coolant flow fields. Because each half is stamped to define the desired reactant flow field, the coolant flow field is defined by the impression of the reactant flow field. As a result, the geometry of traditionally stamped coolant flow fields is have a restricted by the geometry of the reactant flow field, providing non-uniform coolant distribution across the fuel cell stack.